Abstract
Leptospirosis, caused by pathogenic Leptospira, is a zoonosis of global distribution. This infectious disease is mainly transmitted by indirect exposure to urine of asymptomatic animals via the environment. As human cases generally occur after heavy rain, an emerging hypothesis suggests that rainfall re-suspend leptospires together with soil particles. Bacteria are then carried to surface water, where humans get exposed. It is currently assumed that pathogenic leptospires can survive in the environment but do not multiply. However, little is known on their capacity to survive in a soil and freshwater environment. We conducted a systematic review on Leptospira and leptospirosis in the environment in order to collect current knowledge on the lifestyle of Leptospira in soil and water. In total, 86 scientific articles retrieved from online databases or institutional libraries were included in this study. This work identified evidence of survival of Leptospira in the environment but major gaps remain about the survival of virulent species associated with human and animal diseases. Studies providing quantitative data on Leptospira in soil and water are a very recent trend, but must be interpreted with caution because of the uncertainty in the species identification. Several studies mentioned the presence of Leptospira in soils more frequently than in waters, supporting the hypothesis of the soil habitat and dispersion of Leptospira with re-suspended soil particles during heavy rain. In a near future, the growing use of high throughput sequencing will offer new opportunities to improve our understanding of the habitat of Leptospira in the environment. This better insight into the risk of leptospirosis will allow implementing efficient control measures and prevention for the human and animal populations exposed.
Highlights
Pathogenic Leptospira, the etiological agents of leptospirosis, occur worldwide
Several studies mentioned the presence of Leptospira in soils more frequently than in waters, supporting the hypothesis of the soil habitat and dispersion of Leptospira with resuspended soil particles during heavy rain
Leptospirosis had long been known as an environment-borne infection, even before its etiological agent could be identified [5] and the term of “environmental reservoir” of leptospirosis has been proposed for soils in endemic regions [5,6,7,8,9,10,11,12,13,14,15]
Summary
Pathogenic Leptospira, the etiological agents of leptospirosis, occur worldwide. Previous studies have estimated that the disease is responsible for at least 1 million cases and nearly 60,000 deaths annually [1] This bacterial infection is frequently asymptomatic or initially presents as a flu-like febrile illness, making its clinical diagnosis challenging. Indirect contamination through the environment is the most frequent human exposure route. This complex epidemiology makes it a paradigm of a One Health disease. Leptospirosis, caused by pathogenic Leptospira, is a zoonosis of global distribution This infectious disease is mainly transmitted by indirect exposure to urine of asymptomatic animals via the environment. Little is known on their capacity to survive in a soil and freshwater environment
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